The invention relates to an extract-and-insert optical wavelength-division multiplexer for: receiving an incoming multiplex comprising a plurality of wavelength-division multiplexed optical carriers, extracting an extracted multiplex, and inserting a multiplex for insertion in an outgoing multiplex. Each of the multiplex to be inserted and the extracted multiplex comprises a respective plurality of optical carriers transmitted in parallel, i.e. as a wavelength-division multiplex. Each optical carrier can be modulated by a modulating signal which may comprise a plurality of channels in time-division multiplex. Such a multiplexer can be used in particular in optical transmission networks implementing a synchronous digital hierarchy.
French patent application No. 94 06984 in the name of Alcatel CIT describes such a multiplexer comprising:
a first optical broadcaster receiving the incoming multiplex and delivering it from N outlets, where N is the maximum number of wavelengths respectively in the incoming multiplex and in the outgoing multiplex; PA1 a first set of N tunable filters respectively coupled to the N outlets of the first broadcaster to select E extracted carriers and T transmitted carriers in the incoming multiplex where the numbers T and E are variable and no greater than N; PA1 a second optical broadcaster receiving the multiplex to be inserted and delivering it from N outlets; PA1 a second set of N tunable filters for selecting I carriers to be inserted from the carriers constituting the multiplex to be inserted, where the I is variable and no greater than N; PA1 an optical combiner for wavelength-division multiplexing not more than N carriers, thereby making up an outgoing multiplex; PA1 N wavelength converters for supplying the combiner firstly with T new carriers respectively modulated by the signals modulating the T transmitted carriers, and secondly with I new optical carriers respectively modulated by the signals modulating the I carriers to be inserted, I+T being less than or equal to N, the N new carriers having distinct wavelengths; PA1 N two-input and two-output optical switches, each having: PA1 control means for controlling the N optical switches and the 2N tunable filters. PA1 a first stage constituted by a broadcaster and a combiner-broadcaster, the broadcaster receiving an incoming multiplex constituted by four superposed carriers having distinct wavelengths and carrying modulating signals, said broadcaster delivering said multiplexer from four outputs of the broadcaster, the combiner-diffuser receiving four carriers carrying modulating signals and having mutually distinct wavelengths that are optionally identical with those of the incoming multiplex, the combiner-diffuser wavelength-division multiplexing these four carriers to make up a multiplex to be inserted, and then broadcasting a multiplex to be inserted to the four outputs of the combiner-diffuser; PA1 a second stage constituted by four optical switches, two of the optical switches being dedicated to the extracted multiplex and each having two inputs respectively connected to an output of the broadcaster and to an output of the combiner-broadcaster, and two other optical switches being dedicated to the outgoing multiplex and each having two inputs connected respectively to an output of the broadcaster and to an output of the combiner-broadcaster; PA1 a third stage constituted by first and second sets of four tunable filters, a first set being dedicated to the extracted multiplex and having four inputs connected respectively to four outputs of the two switches dedicated to the extracted multiplex and having four outputs respectively supplying four carriers enabling an extracted multiplex to be made up, the second set being dedicated to the outgoing multiplex and having four inputs respectively connected to four outputs of two switches dedicated to the outgoing multiplex and having four outputs respectively supplying four carriers; PA1 a fourth stage constituted by a set of four wavelength converters having four inputs respectively connected to the four outputs of the second set of filters to emit four new carriers modulated by the same modulation signals as the four carriers transmitted by the second set of filters, and enabling an outgoing multiplex to be built up; and PA1 control means for controlling the four optical switches and the eight tunable filters. PA1 a first set of filters each tunable on any one of the possible wavelengths for carriers of the incoming multiplex and of the multiplex to be inserted, so as to select from said carriers at least those carriers which carry signals to be transmitted over the outgoing multiplex; PA1 a second set of filters, each filter being tunable to any one of the possible wavelengths for the carriers of the incoming multiplex and of the multiplex to be inserted, to select from said carriers at least those carriers which carry signals to be transmitted over the extracted multiplex; PA1 and transmission means for transmitting either the incoming multiplex or the multiplex to be inserted to any of the inputs to the first or second sets of filters;
a first input connected to a respective output of a filter of the first set; PA2 a second input connected to a respective output of a filter of the second set; PA2 a first output connected to the input of a respective one of the wavelength converters; and PA2 a second output supplying an extracted carrier to constitute the extracted multiplex; and
That known device makes it possible for the wavelengths of the carriers of the incoming multiplex and the wavelengths of the outgoing multiplex to be selected independently; and it also makes it possible for the wavelengths of the multiplex to be inserted and the wavelengths of the outgoing multiplex to be selected independently. It also makes it possible to broadcast the same signals to a plurality of destinations if each optical switch makes it possible to route a carrier both to the extracted multiplex and to the outgoing multiplex.
European patent application No. 0 592 330 in the name of Alcatel NV describes an optical switching matrix which has the advantage of being strictly non-blocking and which makes it possible to implement an insert and extract optical wavelength-division multiplexer that can be inserted in a both-way optical link (i.e. one link for each transmission direction). For each transmission direction, that optical switching matrix comprises: